Nearby small star has three planets in its habitable region

Atlantic : An exoplanet is commonly found by the telltale dimming of the light of a star as the planet passes in front of it. Earth-sized planets orbiting bright, hot stars like the Sun are nearly impossible to detect, however, because they are so small they don’t block much of the star’s brightness. For that reason, Michaël Gillon of the University of Liège in Belgium decided to look for planets in orbit around the smallest, dimmest stars. Most theories of planetary formation suggest that such stars should not have enough material around them to form planets, but Gillon argued that the theories are based on very few observations. Using the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) located in Chile, Gillon and his colleagues have identified an ultracool red dwarf only 40 light-years away and orbited by three planets. Subsequent observations from TRAPPIST and other observatories have revealed that all three are Earth-sized and are located in the habitable zone—the region around a star where liquid water may exist. Because of the star’s small size and dimness, its habitable zone is much closer to it than the Sun’s habitable zone is to the Sun. The closest two planets orbit the star every 1.5 days and 2.4 days.